In this proposed research we are applying genetic and biochemical approaches to the study of amino acid transport in microorganisms. We are characterizing the three amino acid transport systems that serve, respectively, for leucine, glycine and tryptophan. Leucine is transported by a system that requires leucine-binding proteins and one that is membrane-bound. Glycine and tryptophan are each transported by separate membrane-bound systems. The present study will attempt to determine the similarities and differences in these two types of transport systems. We hope to isolate the transport components from each type of system and purify and characterize them. The leucine transport system appears to consist of a receptor site loosely attached to the membrane and one or more membrane-bound components according to our current genetic and biochemical studies. We are looking into the regulation of leucine transport in bacterial cells and how this regulation influences the overall cell physiology. We are also examining the molecular basis of the sensitivity of bacteria to leucine in the growth medium. The overall goal will be the reconstitution of the isolated components of a transport system into artificial phospholipid vesicles. Experiments of this type should serve as a basis for the study of transport in higher organisms.